package com.exam.alibaba;

import java.util.Scanner;

/**
 * date:
 * description:
 */
public class Solution002 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int ans = 0;
        if(n == 3){
            ans = 1;
            System.out.println(ans);
            return;
        }
        int edges = n / 2 - 1;
        for(int i = 1; i <= edges; i++){
            boolean divisible = (n - i) % 2 == 0;
            if(divisible){
                ans += n;
            }
        }
        System.out.println(ans);
    }
}
